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std::type_info::operator==, std::type_info::operator!=

From cppreference.com
< cpp‎ | types‎ | type info
 
 
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std::type_info
Member functions
type_info::operator==type_info::operator!=
(until C++20)
 
bool operator==( const type_info& rhs ) const;
(until C++11)
bool operator==( const type_info& rhs ) const noexcept;
(since C++11)
(until C++23)
constexpr bool operator==( const type_info& rhs ) const noexcept;
(since C++23)
bool operator!=( const type_info& rhs ) const;
(until C++11)
bool operator!=( const type_info& rhs ) const noexcept;
(since C++11)
(until C++20)

Checks if the objects refer to the same types.

The != operator is synthesized from operator==.

(since C++20)

Contents

[edit] Parameters

rhs - another type information object to compare to

[edit] Return value

true if the comparison operation holds true, false otherwise

[edit] Example

#include <iostream>
#include <typeinfo>
#include <string>
#include <utility>
 
class person
{
  public:
    person(std::string n) : name_(std::move(n)) {}
    virtual const std::string& name() const{ return name_; }
 
  private:
    std::string name_;
};
 
class employee : public person
{
  public:
    employee(std::string n, std::string p)
      : person(std::move(n)), profession_(std::move(p)) {}
 
    const std::string& profession() const { return profession_; }
 
  private:
    std::string profession_;
};
 
void print_info(const person& p)
{
    if(typeid(person) == typeid(p))
    {
        std::cout << p.name() << " is not an employee\n";
    }
    else if(typeid(employee) == typeid(p))
    {
        std::cout << p.name() << " is an employee ";
        auto& emp = dynamic_cast<const employee&>(p);
        std::cout << "who works in " << emp.profession() << '\n';
    }
}
 
int main()
{
    print_info(employee{"Paul","Economics"});
    print_info(person{"Kate"});
 
#   if defined(__cpp_lib_constexpr_typeinfo) // C++23
    if constexpr (typeid(employee) != typeid(person))
    {
        std::cout << "class `employee` != class `person`\n";
    }
#   endif
}

Possible output:

Paul is an employee who works in Economics
Kate is not an employee
class `employee` != class `person`

[edit] See also

checks whether the referred type precedes referred type of another type_info
object in the implementation defined order, i.e. orders the referred types
(public member function) [edit]